Single Point Ground

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Probably the last one to figure this one out, but I installed a 1" copper bus bar and tied every piece of ham equipment to the bus bar through 1" braid. No previous RF feedback issues and everything outside was already lightning-protected, grounded and tied back to the house safety ground.  Still lots of potential for ground loops with coax, power, audio and control connecting all the gear and some audio hum.

With everything tied together audio hum dropped from background level to inaudible.  Took some searching to find a drilled bus bar, but definitely worth the effort.
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Asher - K0AU

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Posted 5 years ago

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KY6LA - Howard, Elmer

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Suggest you read my presentation on how to build a quiet station

https://www.dropbox.com/s/kffp92esffo...

BTW. Much less expensive to use 1/2" copper pipe as your bus bar and much easier to work with pipe.
(Edited)
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Ken - NM9P

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By "Single Point Ground" are you referring to all the ground cables actually going to the same bold on the copper pipe (or very closely so) or merely to the same copper pipe running along the back of the table?  I currently have a 3/4 inch flat braid screwed to the back of my desk with screws about every 8 inches to which I attach my various pieces of equipment.  Is this an invitation to ground loops, and should I change to a pipe with a couple of clamps with everything bolted to the clamps?  I already have some copper pipe that I bought for an antenna project that never materialized.

I have had no problems to date, but then I currently don't run any more than 100 Watts.  The amp will be added after the tower and T-11 go up...
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KY6LA - Howard, Elmer

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I have them all going to the same ground clamp on my ground bus (1/2" copper pipe)

Your approach is an invitation for ground loops.

The ideal design for ground us a star. Yours are not a star.

If the bus is short,... Really not an issue at HF. But 8" is huge at VHF/ UHF
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Ken - NM9P

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Thanks,  That is what I was starting to understand.  My grounding system will be modified as the tower goes up.  I have a couple of new ground rods, but need to get several more - one on each leg of the tower tower, one at the house entry point, one or two outside the shack window, all connected with #6 wire.  I need to buy about 250-300 ft of that stuff plus a bunch of copper braid for ground straps and some more clamps.

Then I need to start putting together the 12 buss for all the wall-wart powered stuff in the shack, and another one for all the other wall warts in the den/TV room.   I may even need to buy or build a higher current 5 Volt supply for all of the 5 Volt stuff.  This stuff could start getting expensive!
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KY6LA - Howard, Elmer

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But it's well worth it to be able to be the first to hear that really weak one that no one else can hear
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Dale KB5VE

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Ken good friend Bill kf5ce retired from the FAA. He was in charge of upkeep on sites. Never had a piece of gear damaged by lightning. First rule he teaches one ground rod on tower! If you use more than one you must be sure each rod is more than their length from any of the others, example 8foot ground rod must be more than 8 feet from any other ground rod. More is not always better because of the danger of ground loop, lightening strikes comes down one ground and back up another if too close. I had some issues with this until I got on Internet and started reading, he was right. Next lightning rod on tower sharpened to a point and change when it is worn down, yes it will happen. Single point grounding of equipment on the inside.
He is a wealth of infromation .
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Asher - K0AU

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Thanks for the link.  Lots of good ideas.  I live in a suburban neighborhood with the usual mix of nieghbors with switching power supplies and pool pumps.  I see -124 dBm average noise level with a 100KHz pan and antennas disconnected.  Just now with my 20-10m antenna connected on 10m (band closed): -118 dBm.  On 20M: - 112 dBm.  I use an Alinco switching power supply with a common 13.8VDC rail to everything except the network switch.  Any likely benefit to changing the PS?
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George Molnar, KF2T, Elmer

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The comments on here are all really good. Your noise seems about right for us in the suburbs. 10m with the band dead with the same setup you mention is -122 dbm. No antenna -124. You might want to try the 400 Hz filter and look at the s-meter (hover over for dbm). No preamps on. I get -118 dbm. Results will vary, but at least you'll have a consistent way of assessing progress.
Good luck!! 

(note - I edited this to reflect "dead band" conditions vs my earlier report of -118 on 10m while there was still propagation)
(Edited)
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Steve W6SDM

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What you did, Asher, is eliminate a ground loop, which can occur when you have ground wires going to several points.  I found that our the hard way as well and I have a copper bus and braided wire going to everything including the computer.

Howard has a great presentation on tracking down noise.  I eliminated a couple of things by watching it and I think I was already pretty nose free at the start.  One thing I did was to set up a 12 volt power bus off my station supply with a rig runner.  Then I tossed all the 12-volt wall warts and ran an Anderson power pole cable to the rig runner.  It got rid of the wall warts and the power strips.
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Steve W6SDM

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What you did, Asher, is eliminate a ground loop, which can occur when you have ground wires going to several points.  I found that our the hard way as well and I have a copper bus and braided wire going to everything including the computer.

Howard has a great presentation on tracking down noise.  I eliminated a couple of things by watching it and I think I was already pretty nose free at the start.  One thing I did was to set up a 12 volt power bus off my station supply with a rig runner.  Then I tossed all the 12-volt wall warts and ran an Anderson power pole cable to the rig runner.  It got rid of the wall warts and the power strips.
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KY6LA - Howard, Elmer

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Switching supplies all generate some Spurs.
Most switching supplies are just giant wall warts.

BTW I seem to recall that there was some way to tune some models of the Alinco's internally to move the Spurs outside of the ham bands.


Easy to see if you have significant Spurs.


Just drag a car battery into the house...run everything off the battery...see if it makes a difference


If so, consign the switcher to the garbage dump or sell it to an unsuspecting ham who is still using a deaf legacy radio if you can't tune the Spurs.


If not, u will be ok
(Edited)
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Paul Christensen, W9AC, Elmer

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No matter how much we try and eliminate ground loops, it's nearly impossible to do so.  With most of our equipment, ground loops are an indispensable part of our stations.  It's more important to establish a low-Z ground point than it is to search out and destroy each ground loop.

Every AC third-wire ground, coax connector, RCA jack, grounded DB connector, 12V negative return, etc. all create ground loops.  If we eliminated all of them we would not have very effective stations.  Go ahead, draw ALL the ground paths in your shack. You may be very surprised to see how many grounds come together in loops.   

Often, there's an attempt to lift the third-wire safety ground at the AC receptacle.  Don't do it.  There isn't a single reputable article in an engineering journal that advocates lifting of the safety ground. 

Nor can we un-ground all the loops created by our coax and RCA connectors.  We need them for effective RF transmission and control.   Just because we bring our chassis grounds to a common ground point does not mean we have eliminated the ground loop.  In fact, we have just added another.  We really need to stay focused on the end objective and not pretend that we're eliminating ground loops with a common ground point.

Paul, W9AC 
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Luis del MOlino

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The worst idea you can have  is installing a single ground for RF.

Just imagine you are succeding and getting part of your precious RF passing through this common ground cable to earth. 

Now you've got the worst of scenarious. The ground cable is now forming part of your radiating antenna, radiating part of your RF.

The RF is radiated inside your shack in transmission and, when in reception, you have a receiving antenna inside your shack, capturing all noise generated in the vicinity. 

Please forget common RF grounds and put ferrite rings in all your common electric protection ground to avoid any RF passing trough any ground cable.

Please keep RF outside of your shack putting a good tension balun up in your dipole or VERTICAL antenna and another one with ferrite Un-Un down on your shack just at the output of your transceiver to avoid the shilding of your coax acting as a vertical antenna and capting your own RF and all noise in the vicinity.

And please forget the commong RF ground cable connected to another earth.


73 Luis EA3OG
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Luis del MOlino

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Thankyou for your support to end with this fantastic myth on the commonn RF ground inside the shack as a solution to resolve RF troubles, when baluns and ununs have proven to be the most simple solution to avoid thiat RF circulating insede your shack.  If you do so, at the same time you get a first class premium consisting in not receiving noise capted by your unfortunate Common RF ground cable.

733 Luis EA3OG
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KY6LA - Howard, Elmer

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WRONG, WRONG WRONG

Suggest you read QST Jan 2015 P 63

RF radiates from EVERYTHING inside your shack.. Not Only the Antenna and Cable but all wires, cables, chassis,power lines and AC Protection ground.

A balan and UNUN can fix common mode currents RADIATING from your antenna cables when transmitting but they will do nothing for the RF Radiating from your radio chassis, your computer, your wall warts, your monitors, you toaster, you oven, you TV, etc etc etc. especially when receiving.

To minimize the RF in the shack, you not only need the balun and/or UNUN but you need to bond all equipment to a common RF Ground Bus.

There are actually 3 different grounding systems to consider when setting up a station.

First is the Electrical Protection Ground (the 3rd or green wire in the AC Circuit).  it is there to protect you in case there is a short from the hot wire to any surface.... this is NOT RF Ground...So you do not want to run your RF Ground to it....

Second is the Tower Protection Ground... this is a ground system near the tower to protect the tower in case of a lightning strike...Many people make the mistake of tying their tower to the re-bar in the concrete thinking it may be ground.. This is very dangerous as I have seen lightning strikes shatter concrete bases when they vaporize the re-bar. -  The lightning protection ground needs to be mechanically connected to the tower to bleed off any lightning hits... it cannot be soldered as a lightning hit will melt the solder..... this is NOT RF Ground

The Third is the RF Ground which I detail in my "How to build a quiet station" presentation.  Interestingly enough Ward Silver has an excellent article on RF Ground on Page 63 Jan 2015 QST which says exact what i said in my presentation..right down to copying my idea of using inexpensive 1/2" copper pipe as your RF Ground Bus.
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Jay / NO5J

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Yep RF grounds, RF on the shield/ground of coax and ground loops. They all have something to do with ground but, they aren't all the same thing. Some people, have difficulty holding onto more than one thought at a time, Flying and falling, are similarly confused  Flying is fun, but when the flying stops suddenly, your falling. which is almost never good, when the falling stops, well then it could be the ground, which is bad.   
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KY6LA - Howard, Elmer

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WRONG!

Single point RF ground is standard engineering practice for all commercial communications systems.

I agree however that you can never put too many toroids on cables and good balanced matching at the antennas will help.
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Ken - NM9P

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Howard,
As I continue to contemplate my grounding system (the tower has been delayed again) and gather ground rods, cables, etc, I have a question...

My tower is about 65 ft from the electrical entrance to the house, and it is about another 50 ft to the shack.  I was planning on running three ground rods spaced around the tower, all looped with #6 copper wire, and then run that to the electrical entrance ground rod, then along the side of the house (slightly buried) to a ground rod or rods outside my shack window, which will also feed a 1/2 inch copper pipe along the back of my desk as a ground bus.

Is #6 copper adequate for this task?  And should I use solid or stranded wire for this?  I want to use the right stuff, but not more than I need because copper is expensive these days!

Thanks for your thoughts,

Ken - NM9P
(Edited)
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KY6LA - Howard, Elmer

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Ken

Sorry about my delay in replying..

I have finally recovered from massive Jet Lag from our latest trip to France followed by too much exercise from 6 days of scuba diving in Nevis and Sint Maarten....

Email me your phone number to ky6la at ky6la dot com so we can talk about this in detail..
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KY6LA - Howard, Elmer

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Ken:

1.Email me your phone number to ky6la at ky6la dot com so we can talk about this in detail..

2.  I would definitely NOT connect the Tower Lightning Protection System Ground to the House AC Protection Ground.  You want to keep a lightning hit to the tower away from the house.

3.  According to the National Electrical Code, Grounding wires should be NO SMALLER than #4 AWG... so #6 AWG is too Small..

4.  Remember when connecting Lightning Protection Systems to make Mechanical NOT Soldered connections as solder will melt and fail from a lightning strike.  Another safe alternative is to thermo-weld the connections.
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Ken - NM9P

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Thanks, Howard,
I'll get back to you after Christmas.
As a pastor, I have a busy week, and then a Funeral on Saturday!
Ken - NM9P
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KY6LA - Howard, Elmer

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No Problem Ken...

Figured this was your busy season...
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KY6LA - Howard, Elmer

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Ken

There are actually 3 different grounding systems to consider when setting up a station.

First is the Electrical Protection Ground (the 3rd or green wire in the AC Circuit).  it is there to protect you in case there is a short from the hot wire to any surface.... this is NOT RF Ground...So you do not want to run your RF Ground to it....

Second is the Tower Protection Ground... this is a ground system near the tower to protect the tower in case of a lightning strike...Many people make the mistake of tying their tower to the re-bar in the concrete thinking it may be ground.. This is very dangerous as I have seen lightning strikes shatter concrete bases when they vaporize the re-bar. -  The lightning protection ground needs to be mechanically connected to the tower to bleed off any lightning hits... it cannot be soldered as a lightning hit will melt the solder..... this is NOT RF Ground

The Third is the RF Ground which I detail in my "How to build a quiet station" presentation.  Interestingly enough Ward Silver has an excellent article on RF Ground on Page 63 Jan 2015 QST which says exact what i said in my presentation..right down to copying my idea of using inexpensive 1/2" copper pipe as your RF Ground Bus.
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Luis del MOlino

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We are not discussing the First Electircal Protection Ground that is mandatory in the shack. Nor the Second, the Tower Protectin Ground that is fundamental against thunderstorms.
What we are discussing here is the Third one, the Common RF ground in the shack. Dont do it.

Lets start from the point you have RF circulating through your station instead of circulating inside of your coaxial cable as it must do. And you try to get it off of your station, off of you mike, your audio amplifiers, sending this RF to earth through a common RF ground cable. Thats Wrong, Wrongm, Wrong. 

First of all, a common RF potentical (tension) in a copper bar in the shack does not exist because RF changes potential (tension) throug any centimeter of cable. 
What you would get now is RF current circulating through this ground RF cable. Now this cable is forming part of your radiating system. Remember it has RF passing through it and, in consequence, it radiates as any other cable with RF.
And in reception, it just makes just the opposite work and now is capting all the RF generated by switching power supplies, devices, etcetera, circulating in all your electrical system of your shack and puting in your radiating system (as receiving antenna)..

Thats when you need the ferrite rings and beads coming in your help with Ununs (downside) and Baluns (upside) avoiding all this happen, avoinding any RF trying to circulate outside the coaxial cable in transmission and IN RECEPTION. It is so simple. 

73 Luis EA3OG

  
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KY6LA - Howard, Elmer

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As a Professional Engineer with more than 1/2 a century of experience designing and building successful communications systems, I will state quite categorically that your pet theory does not stand up to scrutiny of scientific fact nor practical experience.

Balun's and UNUN's will help reduce Common Mode Currents from circulating on your coaxial cables when your are TRANSMITTING but they will do little to reduce the RF in the Shack when receiving nor will they reduce RF from Wall Warts, Monitors, Computers and Radios when receiving.

Common Engineering Practice to reduce RF in the shack is to bond all metal chassis to a common RF Ground Bus.  Here is a copy of a diagram posted in January 2015 QST P 64 by Ward Silver N0AX - who i believe used to be the Technical Editor of QST.  

Needless to say this diagram based on good science totally disagrees with your pet theory. 


 
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KY6LA - Howard, Elmer

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Quite simple - some of your cables in the shack like the ethernet cable connected to the 6300 are resonant at the transmit frequencies and are transferring RF into the Radio...  Ferrites, toroids on ALL the cables and good chasis bonding should cure it...
(Edited)
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KY6LA - Howard, Elmer

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Burt:

Those are NOT the same Cables..

When was the last time you saw an Ethernet Connection to your Icom/Kenwoood or your 5000 radio?

RF in the shack is very much a situational issue rather than a structural issue with the radio...  For example your 6300 RF crashes could be a result of RF ingress into your router or various Ethernet cables connected to your computers...and not the 6300 crashing itself...

I have had Icom and Kenwood and Yaesu Radios which were affected by ingress of RF through various cables until we cleaned them up.
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Luis del MOlino

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Howard:

I am sorry to hear about your insistence in the common groun RF ground does not affect reception, because my experience shows just the contrary. I am already Electronical Engineer and I have been a licenced radioamateur for almost 54 years (in a few days) and I have tried all sort of antennas and grounds and burnt my moustache many times with RF in common RF grounds. Now I do not use them anymore. Only baluns and Ununs and I have forgoten all those USB hangings.

I think you will agree with me that if RF circulates in transmision through a Common RF cable grounded  until a good earth connected to the transceiver it circulates exactly the same oposite way when this cable (and its antenna) is used in reception with the same transceiver.  And this ground RF cable is now inside your shack. Now it forms part of your receivng antenna inside your shack.

Now that you are owner of a Flex 6000 you could be able to see a few dBm changes. Try an MFJ-915 Un-un (plenty of ferrite rings) in the coaxial that leaves your transceiver  and observe the difference with and without the Un-un downside. You cannot see the small difference with an analog S-meter, but you'll see the noise reading changes in some bands related to the physical length of your coaxial cable.

Unfortunately it is not so easy to check this now with the Flex 6000 series compared with the precedent Flex rigs, because the difficult reading of the Flex SmartSDR S-meter that changes so quickly and with an astonishing delay.

It was very easy to see all these differences (with and without) in PowerSDR S-meter because it has an optional "Signal average" meter position. You can see there changes of fractions of S units  Try it. I am the owner of a Flex-1500 and it's the better one for this test. 

If the length of the coaxial is quite short in relation to the wave length of one band, the change is very small, but when it reaches half way length or more, I have seen changes of almost -3 to -6 dBs in noise floor in some bands (20 and upper) in my shack in a crowded small village (houses are one side by side the other here In Spain).  And all this with another balun (a tension one) placed in the base connection of a vertical antenna. 

73 Luis EA3OG
 
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Andrew Russell

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Luis & Howard,

I believe that you are both correct.

We need both a high impedance for common mode currents and a low impedance ground so that the voltage and current on the outside of the coax is low at the transceiver and the antenna and not coupled to the differential mode.

The common ground negates earth currents and voltages adding to the common mode at the radio.

At the antenna balance or choking limits the coupling of the common mode to the antenna.

The balance between grounding and choking will vary with each unique installation.

Andrew de VK5CV

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KY6LA - Howard, Elmer

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I agree Andrew... that is what I have been trying to say... You need ferrites to choke off common mode currents and you need a good RF Ground bus to reduce the voltage of the residual common mode.
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Luis del MOlino

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Andrew and Howard, thanks for your comments.

Anyhow I wish to precise that you cannot have a common RF tension in any way in a copper bar connnecting all devices in a shack because this is a CC concept. Here in RF It's not a question of Ohm's Law but a problem of length.  Remember RF tension changes with every meter on a conductor in HF, and changes in every centimeter in VHF+.
 
Lets say you have a table with 5 feet (1,5 meters) and a copper bar connecting all devices and a very short earht connection just under your own feet in the shack with 3 feets cable (almost 1 meter, the height of the table). That makes a total of 2,5 meters. This is a 1/4 of wave lenght on the 10 meters band.  If you have a very good ground under your own feet with 0 V RF, you'll have a maximum RF tension at the other end of your fantastic common copper ground bar.  And this high RF tension is just at your transceiver ground connection, and you could be in troubles in TX in 10 meters if you do not have placed a balun at your antenna to choke RF outside the coaxial cable. 

The second precision is about the "common" mode current. Commonn to what? This "common" concept applies very well to 2 parallel cables that could carry diferential currents in opposite directions or common currentes circulating in the same sense.  Or both at the same time.

But in a coaxial cable, if you have a current outside the coaxial cable, you do not have this "common" RF current circulating at the same time and the same direction through the inner conductor of the coaxial. So, they do not carry any currents in common. Only the diferential current that carries your RF to the antenna and a posible outside current if no balun is at the antenna connnection. So, we should better speack of "outside coaxial current" and we should forget that absurd word "common" to describe this fenomen so peculiar in coaxial cables, that seems to have three conductors instead ot the phisycal two it has.

Have a nice Christmas
73 Luis EA3OG 
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k3Tim

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Agree Luis that coax is 3 conductors at RF,

1 -  center conductor  
2 - inner shield
3 - outer shield

due to skin effect.  Speaking of skin effect one could use copper foil instead of the water piping.  

Back in the 90's I used a 1//2 inch / 12mm water pipe to form ground bus as being described here   Was able to run a 1kw RTTY station w/o problems.  Ferrite beads helped but some equipment had to have bypass caps installed on external leads.

The Flex 6500 and Flex Control seems bullet proof to RF as it is not having any problems even though the antenna setup here is not so good.
Can't say the same for the keyboard as its going bonkers when Xmt and ferrites helped but not cured.

Merry Christmas to all,

Tim
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Jeffrey Williams

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This is very confusing.  Single point/spaced,  Ground to Common  Ground of box / dont,  No lightning grounds to common, lightning grounds to common ground.

I live in Florida,  Lightning  always strikes.  So close you see colors and your ears ring before you hear the thunder clap.

I am going to use a 20 to 30 ft tilting antenna tower.  It will not be up unless the atmosphere is clear of lightning and the coax will be disconnected.

1.  Should my system ground go to the AC input Box Ground Rod outside my shack?
2.  Should my Lightning arresters  and plate be on that ground rod?
3.   The are 2 ground rods inline hooked to my AC input Box,  does it matter which one I hook to.